This invention relates to a method for manufacturing a display device, and more particularly to a method for manufacturing a display device including an electron emission means and a luminous means excited by electrons emitted from the electron emission means.
A method for manufacturing a display device which has been conventionally carried out in the art will be described with reference to FIG. 8. Apparatus shown in FIG. 8 is constructed so as to carry out vacuum evacuation of a display device. For this purpose, it is adapted to evacuate the display device to a pressure at which sealing of the display device is carried out.
In FIG. 8, a display device 102 is formed by sealedly joining a cathode substrate made of, for example, glass and having a cathode for emitting electrons therefrom arranged thereon and an anode substrate made of, for example, glass and having an anode for capturing the emitted electrons arranged thereon to each other in a manner to be spaced from each other at a predetermined interval. The apparatus for evacuating the display device 102 thus formed includes a chamber 101 which is provided therein with a heater and in which the display device 102 is received for evacuation and a vacuum evacuation unit connected to the chamber 101 and including a head 103 connected to an evacuation tube for evacuating the display device 102. In the prior art shown in FIG. 8, the head 103 is constructed so as to permit the display device 102 to be arranged in the chamber 101.
The head 103 is connected through a valve 104 to a manifold 105, which is then connected through valves 112 and 106 to a dry pump 107. The manifold 105 is also connected to a gate valve 108, which is then connected to a turbo-molecular pump 110. The turbo-molecular pump 110 is connected through a valve 111 to the dry pump 107. Now, the manner of operation of the apparatus thus constructed will be described hereinafter.
First, the display device 102 is received in the chamber 101 and the evacuation tube is connected to the head 103. Then, the valve 112 is rendered open to permit the manifold 105 to communicate with the dry pump 107, so that evacuation of the display device 102 to a rough vacuum may be carried out through the manifold 105, valve 104, head 103 and evacuation tube. The rough evacuation causes a pressure in the display device 102 to be reduced to a certain degree. Then, the valve 112 is closed and the gate valve 108 is rendered open, resulting in the turbo-molecular pump 110 communicating with the manifold 105, so that evacuation of the display device 102 to a vacuum may be accomplished through the manifold 105, valve 104, head 103 and evacuation tube, during which the valve 111 is kept open to back up the turbo-molecular pump 110 by means of the dry pump 107.
Then, the gate valve 108 is rendered open and concurrently the heater is turned on to heat an interior of the chamber 101 to a temperature of about 350.degree. C., resulting in the chamber 101 being kept at about 350.degree. C.
Then, the evacuation is continued for a few or several hours under such conditions, so that the display device 102 may be evacuated to a pressure as low as about 10.sup.-7 Torr and then the evacuation tube is sealedly closed to keep the display device at a high vacuum.
A temperature profile in the process described above, as shown in FIG. 9, is so set that a temperature is increased to about 350.degree. C. by operation of the heater arranged in the chamber 101 after the rough evacuation and then kept at about 350.degree. C. for a few or several hours. Then, the temperature is gradually decreased to a predetermined level while continuing the evacuation, followed by sealing of the evacuation tube. Thus, the display device 102 is evacuated while being subject to baking so as to facilitate discharge of gas from the display device.
Unfortunately, the display device thus manufactured has a disadvantage of being deteriorated in life characteristics (survival rate), although it is evacuated to a high vacuum while being subject to baking. Also, it has another disadvantage that an increased period of time is required for evacuation of the display device to a high vacuum.
The above-described deterioration in life characteristics (survival rate) of the display device would be due to the fact that gas generated in the display device 102 is insufficiently discharged therefrom. Phosphors and electrodes made of various materials which have gas absorbed thereon are arranged in the display device. Unfortunately, even baking fails to permit the gas absorbed on the materials to be satisfactorily discharged therefrom. Thus, the gas is caused to be gradually discharged from the materials when the display device 102 is operated for display after sealing, resulting in polluting an electron emission source and the like arranged in the display device, leading to deterioration in life characteristics (survival rate) of the display device.
Manufacturing of a display device which solves the above-described problems of the prior art is proposed in Japanese Patent Application Laid-Open Publication No. 299129/1990. The techniques proposed are adapted to feed a display device with electricity during vacuum evacuation of the display device, to thereby activate an electron emission source of the display device and concurrently hit anodes with electrons emitted from the electron emission source to discharge gas absorbed on the anodes therefrom.
Unfortunately, the proposed techniques fail to sufficiently discharge gas from the display device, to thereby fail to significantly improve life characteristics of the display device.